PROJECT SUMMARY We propose a collaborative project between HIV and Alzheimer's Disease (AD) laboratories to investigate potential synergy between HIV infection and amyloid ? (A?), a key hallmark of aging and AD, in promoting memory impairment. Half of HIV patients on antiretroviral therapy develop neurocognitive impairments (NCI) despite low HIV brain burdens. Age is the most consistent factor affecting NCI progression. We reproduced HIV-NCI pathogenesis in conventional mice infected with EcoHIV, a mouse-tropic HIV. The MPI in the project, Dr. Arancio, reported that non-synaptotoxic doses of exogenous oA? and Tau, another AD hallmark, cooperate in synaptic dysfunction and memory impairment in mice, suggesting that AD proteins have pathogenic potential at their subclinical concentrations. Our joint preliminary results indicate that similar cooperation occurs after administration of a suboptimal oA? dose to EcoHIV infected mice or in culture or after EcoHIV infection of cognitively normal APP/PS1 mice, a model of endogenous oA? accumulation followed by AD pathology. We propose that HIV and subclinical oA? processes cooperate in disrupting synaptic plasticity to exacerbate HIV- NCI beyond each agent alone. The Specific Aims are to: 1) Define specifics of enhanced HIV-NCI pathogenesis in EcoHIV infected mice accumulating endogenous oA? prior to showing AD pathology. (A) optimize the onset of memory deficits with EcoHIV infection in preclinical APP/PS1 mice; (B) determine HIV-NCI severity at disease onset by infected oA? expressing mice for. If aging hAPP-KI mice, a late onset AD model, reproduce findings in APP/PS1 it will be used in subsequent studies. 2) Using a model from Aim 1, we will conduct next generation RNA sequencing (RNA-seq) in infected mice upon reaching HIV disease state compared to controls to: A) generate transcriptome from hippocampus (HPC), prefrontal cortex (PFC), and striatum (STR), and define biological processes specifically associated with memory defects caused jointly by HIV and oA?; B) confirm some transcripts by RT-QPCR in HPC and STR extracts; and C) conduct limited nuclear-RNA-seq analysis in HPC to assign altered HIV-oA? processes/transcripts to specific cell types. 3) Study molecular mechanisms responsible for promoting HIV-NCI pathogenesis in the setting of naturally produced subclinical levels of human oA? in mice. (A) since both HIV and A? disturb wnt signaling and cause dendritic pruning, examine how HIV infection of myeloid cells works with A? in dysregulating Wnt function in dendritic integrity. B) since EcoHIV downmodulates CaMKII and CREB in mice study potential A?-HIV convergence in oA? dysregulation of the CREB role in synaptic strengthening. Studies will include EcoHIV infection of moderate and late onset AD mice, tests of learning and memory, HPC long-term potentiation HPC synaptodendritic integrity, apoptosis, APP processing, and amyloid pathology system and brain HIV burdens, bioinformatics of mouse brain and select cell types, and use of control non-neuropathogenic EcoHIV? Nef.